The invention is directed to a 180.degree. deflector or a device for deflecting light through 180.degree..
In order to be able to economically realize more complex integrated optical circuits, for example, optical coupling fields on a conventional substrate having a square surface, and in order to construct simple, feed-back integrated optical circuits, a 180.degree.-deflection or bending of the light guided in a strip waveguide is necessary.
Up to the present time, only circularly curved waveguides were examined as a possibility of feeding back or reversing the direction of the light in an integrated optical circuit. Such a waveguide is disclosed in a paper by L. D. Hutcheson, I. A. White, and J. J. Burke, "Losses in diffused LiNbO.sub.3 waveguides by directional changes", Digest of Topical Meeting on Integrated and Guided Wave Optics, Incline Village, Jan. 28-30, 1980, Paper WB 2. The inevitably occurring emission losses decrease with an increasing difference of the index of refraction between the waveguide and an external medium and the losses are dependent upon the waveguide cross-sectional dimensions, the wavelengths and the radius of curvature of the waveguide. The cross-sectional dimensions can only be slightly varied for the monomode operation of unsymmetrical waveguides utilizing a fixed light wavelength. The index of refraction difference between waveguides, which have resulted through diffusion of titanium into a lithium niobate and the lithium niobate substrate lie between 0.005 and 0.01. For low losses, which are approximately 0.5 dB for a 180.degree. deflection, a minimum radius of curvature of several centimeters is required. If one realizes the small width of the integrated optical components, which widths, for example, for a directional coupler amounts to approximately 30 .mu.m with an overall length of 6 mm, then it can be recognized that the radius of curvature of several centimeters is impractical and signifies a waste of usable substrate surface. The entire system of problems of the topography of integrated optical circuits has been left out of consideration up to the present time. A mere reduction of the radius of curvature of the waveguides, which is formed by diffusing titanium into a lithium niobate substrate, would cause such great losses due to emission of radiation for the guided wave, that other, space-saving solutions must be found for the purpose of achieving an optimum utilization of the substrate surface.